How does the brain and body physically react to hunger?

Brain:

* Hypothalamus: The hypothalamus is a brain region that plays a crucial role in regulating hunger and appetite. It contains two important nuclei:

1. Lateral hypothalamus (LH): The LH is involved in stimulating hunger and food intake. When LH neurons are stimulated, an individual is more likely to eat.

2. Ventromedial hypothalamus (VMH): The VMH is responsible for suppressing hunger and promoting feelings of fullness. Activation of VMH neurons leads to decreased food intake.

* Ghrelin and leptin: These two hormones primarily regulate communication between the body and the hypothalamus regarding hunger cues:

1. Ghrelin: Produced mainly by the stomach, ghrelin levels rise before meals and fall after a meal. It signals the hypothalamus to increase hunger.

2. Leptin: Produced by fat cells, leptin signals satiety and fullness to the hypothalamus. Higher levels of leptin lead to reduced food intake.

Body:

* Stomach: Hunger pangs, commonly referred to as growling stomachs, originate in the stomach. When the stomach is empty or partially filled, its muscles contract and relax vigorously. These movements create sounds due to the mixing of air and digestive fluids in the stomach.

* Gut hormones: The gut produces various hormones that influence hunger, including:

1. Peptide YY (PYY): Released after eating, PYY promotes a feeling of fullness.

2. Glucagon-like peptide-1 (GLP-1): Like PYY, GLP-1 is also released after eating and can slow gastric emptying, contributing to the feeling of fullness.

* Insulin: Insulin is a hormone produced by the pancreas in response to increased glucose levels in the bloodstream. It helps transport glucose from the blood to cells for energy production. As insulin levels rise after eating, hunger decreases.